Briquetting of coals



United States Patent 3,094,399 BRIQUETTING 0F COALS Kenneth Ernest Barton Macqueen, Maghull, England,

assignor, by mesne assignments, to American Cyanamid Company, New York, N.Y., a corporation of Maine No Drawing. Filed Mar. 2, 1960, Ser. No. 12,253 Claims priority, application Great Britain Mar. 10, 1959 9 Claims. (Cl. 44--23) This invention relates to the briquetting of coal and more particularly to the manufacture of carbonized coal briquettes suitable for use as smokeless and/or metallurgical fuel.

In the carbonization of coal briquettes the Swelling characteristics of the coal require to be taken into account, as it has been found in practice that satisfactory carbonized briquettes cannot be produced unless the coal inherently possesses the desired swelling characteristics or unless the swelling characteristics are suitably modified before carbonization.

Coal swelling numbers, and the process whereby such numbers are determined, are defined in British Standards Specification No. 1016 of 1942. Tests over large varieties and types of coal have shown that normally a satisfactory carbonized briquette cannot be produced from coal having a swelling number in excess of B.S. 2%. Very few coals naturally possess the required swelling properties, and their availability for briquetting is limited. Goals of higher swelling numbers are rather more readily available, particularly in the form of slack or small coal which is not in great demand and of which large reserve stocks exist. The small size of the coal is of no detriment, as coal for briquetting requires preliminary grinding, and accordingly small coal is eminently suitable for briquetting if its swelling properties are also suitable or have previously been suitably modified.

In my earlier filed copending application, United States Patent application Serial No. 849,708, filed October 30, 1959, I have described a process for briquetting coal having a swelling number in excess of B.S. 1 (as defined in B.S.S. No. 1016/ 1942) wherein the swelling number of the coal is first reduced to the order of B.S. 1 by mixing the coal, in particulate form, with a predetermined proportion of tar and allowing the mixture to age for a short period before it is mixed with a suitable binder and formed into raw briquette bodies of the desired shape or size. During the period of aging in the tar and coal mixture, the swelling number of the coal is reduced to the vicinity of B.S. 1 by the action of the tar. Briquettes made from coal of this swelling number can be carbonized in a retort without the deformation of the briquettes or damage to the retort which would undoubtedly occur if an attempt was made to carbonize briquettes formed from coal having a swelling number very much in excess of B.S. 1.

While the above-referred to procedure is satisfactory for coals having swelling numbers up to B.S. 4, in the case of coals having swelling numbers of B.S. 5 or more the proportion of tar required is so great that the resultant tar/coal mixture is excessively plastic and is unsuitable for subsequent formation into briquettes which will retain their shape.

It is an object of the present invention to provide a process whereby the swelling characteristics of coals having a B.S. number of 5 or greater are reduced to a tolerable amount and further to provide a process whereby briquettes made from said coals are able to resist a substantial head-load during car-bonization.

In the present specification and claims the term oxidation means the heat treatment of coal in the presence of an oxidizing agent whereby its swelling number is reduced.

Patented June 18, 1963 According to the invention, a process for manufacturing coal briquettes broadly comprises the steps of reducing a quantity of coal having a swelling number of at least B.S. 5 to a predetermined particulate size, subjecting it to heat oxidation to reduce the swelling number thereof to a predetermined value in excess of B.S. 1, intimately admixing the thus-treated coal with a predetermined quantity of crude tar or a distillation fraction thereof, permitting the mixture to age for a predetermined period, then admixing the mixture with a suitable binder and forming the plastic aggregate thus obtained into briquettes, the predetermined quantity of crude tar and the aging period being sufiicient to cause a still further reduction of the swelling number of the partially oxidized particulate coal to the order of at least B.S. 2 /2.

Whilst heat oxidation plus tar, or a constituent thereof, will, in many cases, alone produce the desired results, a still further reduction is made possible by the addition to the tar, or the constituent thereof, of a small proportion of quicklime. Quicklime alone, without tar or one of its constituents, is relatively ineffective in reducing the swelling number of coal unless such a high proportion of lime is added as to increase the ash content of the resultant briquette to an unacceptable degree.

In carrying out the present process, coal having a swelling number of B.S. 5 or greater is pulverized and dried, if necessary. It is then conveyed to an oxidizer wherein its swelling number is reduced to a B.S. value of preferably between 3 to 5.

The preferred apparatus for heat oxidizing the coal is described in British Patent 724,774, which specification is hereby made a part of this specification. In said patent is described a heat oxidizing process and apparatus whereby ooal particles are heated to an elevated temperature preferably within the plastic range of the coal, for a period of time sufiicient to lower the swelling number of the coal to the order of B.S. 1. This is done by fluidizing suitably ground and dried coal into a stream of hot air, preferably by means of a Fuller-Kenyon pump unit, and forcing the resulting stream of fluidized coal through an oxidizing coal immediately followed by a cooling coil. Proportions ranging from 8 pounds of coal per pound of air to 12-15 pounds of coal per pound of air have been used with success. In the oxidizing coil the coal is heated to a temperature within its plastic range (i.e., about 350- 500 C.) for a time of less than a minute and preferably about 10-15 seconds and is then cooled, preferably to about F.

However, according to the present invention the heat oxidation is terminated when the swelling number of the coal has been reduced preferably to between B.S. 3-5. This may be accomplished by decreasing the residence time wherein the coal and oxidizing medium are in contact. Since the contact time may vary from coal to coal, depending upon the initial swelling value and other factors, 1t will be necessary to vary the contact period with different coals. However, I have found a residence time of less than a minute to be satisfactory when using the process of the aforementioned British patent.

After leaving the oxidizer, the coal is allowed to cool and is then intimately mixed with a quantity of crude tar, preferably a tar obtained from the low temperature carbonization of coal. The quantity of tar required depends upon the swelling number to which the coal has been reduced by the partial oxidation and at a swelling number of B.S. 3-4 will be in the region of 10% by weight of the coal. The mixing vessel may be suitably warmed and the mixing operation be either continuous or batchwlse.

Provided that the mixing has been thorough, the tar reacts upon the coal in the order of five to ten minutes u to reduce its swelling number to BS. 2 /2 or below. The mixture is then ready for mixing with a suitable binder and for forming into briquette shapes in a rotary, reciprocating or extrusion briquette press of any suitable known type.

While it is desirable that the swelling number of the coal be reduced to a value B.S. 1-2, I have found that a coal having a value up to BS. 2 /2 is suitable for subsequent briquetting and carbonizing.

The binder may be of any kind known to be suitable for briquetting and should hold together the shapes formed in the briquetting press and should impart sufiicient strength to them so that they will withstand normal handling and storage whilst in their raw state. It should also be such that it will not soften appreciably during carbonization of the briquettes, so that they do not become deformed under heat or pressure in the retort. One suitable binder is pitch.

From the briquetting press the raw briquettes may be passed directly to the carbonizing retort or they may be stored for subsequent carbonization. If desired, they may be burned in their raw state.

Set forth in Table I below is data showing the reduction of coals having a high swelling number by the process of this invention. In all cases the original coal was oxidized by the above-described heat oxidation method and then subsequently treated with tar and lime or distillation constituents of crude tar and lime.

Table I Coal Grade 601, B.S.#

New Stubbins, B.S.#

10% Gas Works Tar+1% lime..- 10% o-cresol Fraction -160 C.: I

Acetonitrile (C H N) I Benzene (C H Carbon disulphide (CS Cyclopentadiene (C H l 2z4-lutidine (C H N) 2:6-lutidine (CqHgN) u-Picoline fl-Picoline (CsHqN) v-Picoline c fl N Pyridine (C H N) Styrene (C H Thiophen (C H S) Toluene (C H o-Xylene (CgHm) m-Xylene (CgHm) P' a m) Fraction 160205 C.:

2:4:6-colli'dine (C H N) Coumarone (C H O) o-Cresol (C H O) m-Cresol (C H 0) p-Cresol (CqHgO) Dicyclopentadiene (C H Indene (C H Mesitylene (C H Phenol Pseudocumene (C H 2,6-xylen0l(meta-2) (C H O) Fraction 205230 C.:

o-Ethyl phenol (C H O) 4 m-Ethyl phenol (C H O) p-Ethyl phenol (C H O) Naphthalene (C H 2,3-xylenol(ortho-3) (C H O) 3,4-xylenol(ortho-4) (C l-I 0) 2,4-xylenol(meta-4) (C H O) 3,5-xyleno1(meta-5) (C H O) 2,5-Xylenol(para) (C H O) Fraction 230-290 C.:

Acenaphthene (C H Catechol; pyrocatechol (C H O 2:3 dimethyl naphthalene (C H 1:6 dimethyl naphthalene (C H 1:7 dimethyl naphthalene (C H 2:6 dimethyl naphthalene (C H 2:7 dimethyl naphthalene (C H p y 12 1o) Diphenylene oxide (C H O) Indole (C H- N) Isoquinoline (C H N) Lepidine (C H N) 3-methyl-5-ethyl-phenol (C H O) 2-methyl indole (C H N) 7-methyl indole (CQHQN) a-Methyl naphthalene (C H B naphthalene (C1 1H 10) a-Naphthol (C H O) Quinaldine (CloHgN) ,Quinolzhydroquinone (C H O) Quinoline (C H N) Resorcinol (C H O Skatole (C H N) Fraction 290-350 C.:

Acridine (C H N) Anthracene (0141110) iCarbazole (C H N) Fluorene (C I-I B-Naphthol (C H O) Phenanthrene (C H Pyrogallol (C H O) I have found that treating a coal having a swelling value of BS. 3 /2 with any of the above distillation fractions will lower the swelling number to BS. 1%.

The precise amount of tar required to reduce the swelling number of the coal to BS. 2 /2 or less will previously have been determined by tests. Generally, I have found on the order of 5-15% to be satisfactory. Regarding the quicklime, I find an amount on the order of 1-2% to be suitable. 2

ln the mixing vessel the coal, lime and tar, or tar constituent, are thoroughly mixed until an intimate mixture has been obtained and at the end of five to ten minutes or so the tar, or tar constituent, and the lime have reacted upon the coal so that its swelling number has been reduced to at least 2 /2.

The mixture is then mixed with a suitable binder, such as pitch, as known in the briquetting art, and is formed into suitable raw briquette shapes in a rotary, reciprocating or extrusion press of any of the types known for briquetting. The binder need not necessarily be a pitch binder although pitch is the one most commonly used in the art, but it requires to be such as to hold together the coal/tar/lime shapes delivered from the press and to retain them in shape during handling and storage prior to carbonization. The binder should not soften appreciably during carbonization.

The briquettes so formed may be used in their raw state or may subsequently be carbonized in the known manner for use as smokeless or metallurgical fuel.

Raw briquette shapes formed in accordance with the present invention show good ability to stand the head loads to which they would be subjected during carbonization in a vertical retort, wherein the lowermost briquettes have to support the weight of the briquettes higher in the i retort. Using coal of rank 602 (B.S. No. 6 /2) the following head load test results have been obtained:

1. A process for manufacturing coal compactions from bituminous coal comprising the steps of heat oxidizing finely divided bituminous coal having a swelling number of at least B.S. 5 by reacting said coal with oxygen while in the fluidized state at a temperature within the plastic range of the coal and for a time of less than one minute but sufiicient to reduce the swelling number to a value above 3.8. 1, admixing the heat oxidized coal with about 5-15% by weight of an aromatic composition selected from the group consisting of crude tar having a substantial tar acid content and distillation fractions of the crude tar, aging the mixture for about five to ten minutes until the swelling number of the mass has been reduced to at least BS. 2 /2, admixing the coal/ tar mixture and up to about of a carbonaceous binder and forming the resultant mixture into compactions of the desired size and shape.

2. A process according to claim 1, wherein the aromatic 6 composition is present in an amount of 5 to 15% by weight of the coal.

3. A process according to claim 1, wherein the aromatic composition is present in an amount of about 10% by weight of the coal.

4. A process according to claim 1, wherein from about 1 to 2% of quicklime is present in the heat oxidized coalaromatic composition mixture.

5. A process according to claim 4, wherein the distillation fraction of the crude tar is from C.205 C.

6. A process according to claim 4, wherein the distillation fraction of the crude tar is from 205 C.230 C.

7. A process according to claim 4, wherein the distillation fraction of the crude tar is from 230 C.290 C.

8. A process according to claim 4, wherein the distillation fraction of the crude tar is from 290 C.-350 C.

9. A process of claim 1, wherein the coal compactions are subsequently carbonized.

References Cited in the file of this patent UNITED STATES PATENTS 1,283,310 Rodman Oct. 29, 1918 1,576,253 Summers Mar. 9, 1926 2,164,933 Maurel July 4, 1939 2,314,641 Wolf Mar. 23, 1943 2,661,326 Stillman Dec. 1, 1953 2,834,660 Eisenhut May 13, 1958 FOREIGN PATENTS 724,774 Great Britain Feb. 23, 1955 

1. A PROCESS FOR MANUFACTURING COAL COMPACTIONS FROM BITUMINOUS COAL COMPRISING THE STEPS OF HEAT OXIDIZING FINELY DIVIDED BITUMINOUS COAL HAVING A SWELLING NUMBER OF AT LEAST B.S. 5 BY REACTING SAID COAL WITH OXYGEN WHILE IN THE FLUDIZED STATE AT A TEMPERATURE WITHIN THE PLASTIC RANGE OF THE COAL AND FOR A TIME OF LESS THAN ONE MINUTE BUT SUFFICIENT TO REDUCE THE SWELLING NUMBER TO A VALUE ABOVE B.S. 1, ADMIXING THE HEAT OXIDIZED COAL WITH ABOUT 5-15% BY WEIGHT OF AN AROMATIC COMPOSITION SELECTED FROM THE GROUP CONSISTING OF CRUDE TAR HAVING A SUBSTANTIAL TAR ACID CONTENT AND DISTILLATION FRACTIONS OF THE CRUDE TAR, AGING THE MIXTURE FOR ABOUT FIVE TO TEN MINUTES UNTIL THE SWELLING NUMBER OF THE MASS HAS BEEN REDUCED TO AT LEAST B.S. 2112, ADMIXING THE COAL/TAR MIXTURE AND UP TO ABOUT 10% OF A CARBONACEOUS BINDER AND FORMING THE RESULTANT MIXTURE INTO COMPACTIONS OF THE DESIRED SIZE AND SHAPE. 